1. Field of the Invention
The present invention relates to an image forming apparatus. More specifically, the present invention relates to an image forming apparatus having a gear and a coil spring.
2. Background Information
Heat transfer printers are known as an example of a conventional image forming apparatus. Such heat transfer printer generally has a feed roller and a press roller, between which a paper is to be conveyed. The feed roller is rotated by a feed roller gear, to which rotational torque is transmitted from a motor. The feed roller gear further transmits the rotational torque to an oscillating gear via a pivot arm.
An example of the feed roller gear 113 and the oscillating gear 118 are shown in FIGS. 10-13. Also, as shown in FIGS. 10 through 13, the feed roller gear 113 is provided with a feed roller gear portion 113a for meshing with a small gear 118a of the oscillating gear 118, and a D-shaped mounting hole 113b into which a gear insertion unit 102a of the feed roller 102 is inserted.
As shown in FIG. 13, the pivot arm 114 is provided with an oscillating gear support axle 114a for pivotably supporting an oscillating gear bearing 118c of the oscillating gear 118; a pivoting arm hole 114b into which the feed roller 102 is rotatably inserted; and a boss unit 114c (see FIG. 10) for controlling the amount of pivoting of the pivot arm 114 by interlocking with a control element. A groove for mounting a retaining washer 119 is provided at the top of the oscillating gear support axle 114a of the pivot arm 114.
Also, as shown in FIG. 13, a compressed coil spring 115 is inserted between the pivot arm 114 and the oscillating gear 118 to hinder the pivoting of the oscillating gear 118 by pressing the pivot arm 114 and the oscillating gear 118 in the thrust direction (axial direction) via felts 116 and 117. The oscillating gear 118 is moved in the direction of rotation of the feed roller gear 113 during the rotation of the feed roller gear 113. Accordingly, the pivot arm 114 on which the oscillating gear 118 is mounted therefore pivots as well.
Also, as shown in FIG. 12, the felts 116 and 117 are provided for preventing the pivot arm 114 and the oscillating gear 118 from coming into direct contact with the compressed coil spring 115. It is thereby possible to prevent abrasions on the top surface of the pivot arm 114 and the bottom surface of the oscillating gear 118.
Also, as shown in FIG. 13, the oscillating gear 118 is provided with a small gear 118a for meshing with the feed roller gear 113, a large gear 118b for meshing with still another gear, and an oscillating gear bearing 118c into which an oscillating gear support axle 114a of the pivot arm 114 is inserted. The retaining washer 119 for preventing the oscillating gear 118 from falling out is mounted on the distal end of the oscillating gear support axle 114a of the pivot arm 114.
Since the pivot arm 114 shown in FIGS. 10 through 13 is configured to pivot by the resistance from the axial (thrust-wise) (frictional force) load of the compressed coil spring 115, the retaining washer 119 is needed for preventing the oscillating gear 118 from coming loose. Furthermore, the felts 116 and 117 are needed to prevent abrasions on the pivot arm 114 and the oscillating gear 118. As a result, the number of components increases. Furthermore, there is a need form a groove in the oscillating gear support axle 114a of the pivot arm 114 for mounting the retaining washer 119. Thus, it takes long time to assemble this structure.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved gear support structure for the image forming apparatus that overcomes the problems of the conventional art. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.